In the prior art, many lids are provided with a separate structure configured for opening and closing an outlet so that liquid in a container can flow out from the outlet of the lid. The lid and the cup thereof, which can be opened and closed by one hand, have also been developed. A metal elastic member such as torsion spring is usually used as a reset member of the lid to form a seal. However, the metal elastic member can lose its resilience over time, resulting in an inadequate reset function and seal.